Congress recently introduced a bill that would permit pharmacists and patients to import prescription drugs from Canada.

The policy could harm vulnerable patients, especially those persons living with HIV disease or who are at risk of acquiring it, by introducing counterfeit medications into the U.S. drug supply chain and jeopardizing drug discovery.

Lawmakers hoping to import prescription drugs from Canada have good intentions: They want to make medication more affordable stateside. And drugs do tend to be cheaper in Canada.

But monetary savings can come with a cost — patient safety. Legalizing Canadian drug imports increases the risk of unsafe counterfeit drugs infiltrating the American prescription drug supply.

Counterfeit medicines saturate global drug markets. More than 10 percent of the global supply chain of medicines is counterfeit, according to the World Health Organization. And when it comes to online drug suppliers, 96 percent of online pharmacies violate U.S. pharmacy laws.

In addition to containing inactive and ineffective ingredients, counterfeit drugs also can possess hazardous ingredients such as rat poison, antifreeze and even paint thinner.

Counterfeit HIV/AIDS medicines are particularly rampant. Kenyan and Tanzanian health authorities have each uncovered counterfeit HIV medications. Counterfeit versions of an HIV treatment even found their way into the United Kingdom’s drug supply.

And despite having the world’s toughest regulatory system for drugs, the United States still has battled its share of counterfeit HIV medications. In 2013, a New York pharmacist reportedly made $2.6 million from repackaging black market HIV drugs and selling them to customers as if they were FDA-approved. Since 2006, at least 86 people in the United States have been charged with selling black market medications prescribed to patients living with HIV/AIDS.

The U.S. Food and Drug Administration is the gold standard when it comes to regulating medications and protecting patients. Canada’s weaker regulatory laws mean there is a greater possibility for adulterated, substandard products to enter the U.S. health care system. This is why FDA officials have repeatedly warned lawmakers against importing drugs from foreign countries, including Canada.

Online pharmacies can be very problematic for individuals seeking alternative ways to obtain traditional care or HIV-prevention services. A good example would be with Truvada, which is both an HIV treatment medication for HIV-positive people and a “pre-exposure prophylaxis” for HIV-negative people. Often referred to as PrEP, Truvada is incredibly effective at reducing a person’s chance of contracting HIV. But it’s only effective if the pill truly has all the active ingredients. With online pharmacies, the integrity of medicines can be, too often, in doubt.

The same logic holds true for people buying medications from online, unvetted pharmacies for other more common sexually transmitted diseases, like gonorrhea or chlamydia. Shacking up with an unknown, unlicensed pharmacy makes everyone less safe.

Sadly, drug importation also threatens more than just the health and lives of vulnerable patients. It also damages the innovation pipeline for new medicines.

Canada’s drugs are cheaper because the government imposes price controls on medicines. If the United States were to import these medicines, then it indirectly would import price controls.

Biopharmaceutical companies can’t make new drugs if they’re unable to sell them at market price. Developing a new drug is a hugely time-consuming and expensive process. It takes an average of 12 years and billions of dollars to bring a single drug to market in the United States.

Without the ability for drug developers to recoup development costs, there’s little incentive to make such massive, risky investments into drug development.

That’s especially bad news for HIV/AIDS patients. Drug innovation has helped transform HIV/AIDS from a deadly diagnosis to a manageable disease. Americans with the illness live longer and healthier lives than ever before thanks to incremental gains over decades of drug development. Research firms have already invented medicines that effectively prevent people from contracting the virus. And scientists are hard at work developing medications that could cure the disease entirely, not just treat it.

But permitting drug imports would make it increasingly difficult for drug manufacturers to recoup their development costs, thereby discouraging investment.

Drug prices are not the only costs to consider with drug importation. Passing the proposed legislation would aggravate the flow of counterfeit drugs into the U.S. prescription drug market and seriously limit companies’ ability to create new therapies.